The Detroit Lions signed 11 undrafted free agents following this year's NFL draft, and hopes are high that among that group are a handful of players that can make an impact, now or later.

Expecting any of them to become big-time contributors in 2013 is unrealistic though. Just look at last season. Of the 13 UFAs the Lions signed, three went to the practice squad and only one made the active roster.

That was Kellen Moore, who impacted the Lions as much as I did.

Finding a player that can develop into a solid pro in the next year or two is the goal. Ricardo Silva is a perfect example. He was an undrafted free agent in 2011 and he started six games last season and looks to be a valuable backup this year as well.

There are players from this year's group of UFAs that could turn out to be gems as well.

5. Darren Keyton, C, Central Michigan

Darren Keyton wasn't in the first batch of undrafted free agents the Lions signed following this year's draft.

He was added several weeks later to very little fanfare.

That's ironic since he represents the potential answer to one of the biggest questions Lions fans are currently asking: Who is going to replace Dominic Raiola?

According to ESPN, the Lions have only two centers on their roster, Raiola and Keyton.

Raiola is in his final year with Detroit and the Lions need to start grooming someone to replace him. At this point that someone is not Bill Nagy. He hasn't shown enough durability to be considered a viable option.

Therefore, Keyton might be the best option the Lions have. According to Mlive.com, he started all 13 games at right guard for the Chippewas last season, but he played center his junior year.

The knock against Raiola has always been that he's too small and gets knocked back to often.

At 6'3", 305 pounds, that wouldn't happen to Keyton. He simply needs to prove that he can match Dom's intelligence and intensity.

He's got a long way to go, and training camp will ultimately determine if he's an option or not, but given the Lions needs at the position, Keyton is in the perfect situation to succeed.

4. Steven Miller, RB, Appalachian State

The Lions already have one running back on their roster who used the giant chip on his shoulder to excel in the NFL.

Joique Bell was largely overlooked and underrated for two years. He went undrafted in 2010 despite a great college career and languished on practice squads until the Lions gave him a chance last season.

The rest is history.

The Lions might have another runner on their roster determined to turn past slights into future success—Steven Miller.

Miller has been overlooked his entire football career because of his diminutive size. At 5'7" and 172 pounds he doesn't exactly have the prototypical NFL body. However with a 43" vertical and sub-4.4 second speed in the 40-yard dash, the Lions were willing to give him a chance.

As the Detroit News' Terry Foster reported, Miller has succeeded at every level he's played. His senior year at Appalachian State Miller rushed for 1,368 yards on 239 carries (5.7 yards per carry) and ran for 11 touchdowns his senior season. He also caught 34 passes for 377 yards and four touchdowns.He is a burner in the mold of Darren Sproles or Jahvid Best, but no one should expect him to take over for Reggie Bush any time soon.

He's got great talent and potential, but preseason games might be the only chance fans get to see it this year. He'll either be relegated to the practice squad, or there's a slim chance he could be used in the return game.

This year's depth at running back is simply too great for him to make an impact.

One thing is for sure, Miller is determined to be the hardest worker the football field, as he told Foster:

They are going to see a player that is going to give 200 percent, no matter. I know I am going to make mistakes. I understand that. But I am going to bounce back regardless of what happens. These coaches already have an idea I am one of the hardest working guys here. If not, then it is going to fuel me to show them I am one of the hardest workers here.

3. Austin Holtz, OT, Ball State

Speaking of determination and work ethic, if that's what it is going to take to make the Lions roster then Austin Holtz will have as good a chance as anyone.

At Ball State, Holtz gained 45 pounds to transform himself into a dominating offensive tackle, and he didn't do it by shoving pizza's down his gullet either.

According to Tom Davis of the News Sentinel, Holtz worked daily with Ball State's strength and conditioning coach Dave Feeley to gain muscle mass. Because Holtz needed to hold down a steady job, workouts were held at 5 a.m. each day.

Feeley says that Holtz never wavered or complained and was successful at adding the weight. In the process he became a much better player on the field.

In fact he was All-Mid-American Conference's first team his senior year.

We all know Lions' head coach Jim Schwartz love's these underdog-type players who simply outwork the guy next to them to be successful. Holtz has certainly demonstrated that quality, and if he continues to do so, he might have a bright future in Detroit.